Meta-analysis of primary producer amino acid δ\u3csup\u3e15\u3c/sup\u3eN values and their influence on trophic position estimation

Compound-specific stable isotope analysis of individual amino acids (CSIA-AA) has emerged as a transformative approach to estimate consumer trophic positions (TPCSIA) that are internally indexed to primary producer nitrogen isotope baselines. Central to accurate TPCSIA estimation is an understanding of beta (β) values—the differences between trophic and source AA δ15N values in the primary producers at the base of a consumers’ food web. Growing evidence suggests higher taxonomic and tissue-specific β value variability than typically appreciated. This meta-analysis fulfills a pressing need to comprehensively evaluate relevant sources of β value variability and its contribution to TPCSIA uncertainty. We first synthesized all published primary producer AA δ15N data to investigate ecologically relevant sources of variability (e.g., taxonomy, tissue type, habitat type, mode of photosynthesis). We then reviewed the biogeochemical mechanisms underpinning AA δ15N and β value variability. Lastly, we evaluated the sensitivity of TPCSIA estimates to uncertainty in mean βGlx-Phe values and Glx-Phe trophic discrimination factors (TDFGlx-Phe). We show that variation in βGlx-Phe values is two times greater than previously considered, with degree of vascularization, not habitat type (terrestrial vs. aquatic), providing the greatest source of variability (vascular autotroph = –6.6 ± 3.4‰; non-vascular autotroph = +3.3 ± 1.8‰). Within vascular plants, tissue type secondarily contributed to βGlx-Phe value variability, but we found no clear distinction among C3, C4, and CAM plant βGlx-Phe values. Notably, we found that vascular plant βGlx-Lysvalues (+2.5 ± 1.6‰) are considerably less variable than βGlx-Phe values, making Lys a useful AA tracer of primary production sources in terrestrial systems. Our multi-trophic level sensitivity analyses demonstrate that TPCSIA estimates are highly sensitive to changes in both βGlx-Phe and TDFGlx-Phe values but that the relative influence of β values dissipates at higher trophic levels. Our results highlight that primary producer β values are integral to accurate trophic position estimation. We outline four key recommendations for identifying, constraining, and accounting for β value variability to improve TPCSIA estimation accuracy and precision moving forward. We must ultimately expand libraries of primary producer AA δ15N values to better understand mechanistic drivers of β value variation

Price Discovery and the Accuracy of Consolidated Data Feeds in the U.S. Equity Markets

Both the scientific community and the popular press have paid much attention to the speed of the Securities Information Processor, the data feed consolidating all trades and quotes across the US stock market. Rather than the speed of the Securities Information Processor, or SIP, we focus here on its accuracy. Relying on Trade and Quote data, we provide various measures of SIP latency relative to high-speed data feeds between exchanges, known as direct feeds. We use first differences to highlight not only the divergence between the direct feeds and the SIP, but also the fundamental inaccuracy of the SIP. We find that as many as 60 percent or more of trades are reported out of sequence for stocks with high trade volume, therefore skewing simple measures such as returns. While not yet definitive, this analysis supports our preliminary conclusion that the underlying infrastructure of the SIP is currently unable to keep pace with the trading activity in today's stock market.Comment: 18 pages, 20 figures, 2 table

Major shifts in nutrient and phytoplankton dynamics in the North Pacific Subtropical Gyre over the last 5000 years revealed by high-resolution proteinaceous deep-sea coral δ\u3csup\u3e15\u3c/sup\u3eN and δ\u3csup\u3e13\u3c/sup\u3eC records

The North Pacific Subtropical Gyre (NPSG) is the largest continuous ecosystem on Earth and is a critical component of global oceanic biogeochemical cycling and carbon sequestration. We report here multi-millennial-scale, sub-decadal-resolution records of bulk stable nitrogen (δ15N) and carbon (δ13C) isotope records from proteinaceous deep-sea corals. Data from three Kulamanamana haumeaae specimens from the main Hawaiian Islands extend the coral-based time-series back ∼5000 yrs for the NPSG and bypass constraints of low resolution sediment cores in this oligotrophic ocean region. We interpret these records in terms of shifting biogeochemical cycles and plankton community structure, with a main goal of placing the extraordinarily rapid ecosystem biogeochemical changes documented by recent coral records during the Anthropocene in a context of broader Late-Holocene variability. During intervals where new data overlaps with previous records, there is strong correspondence in isotope values, indicating that this older data represents a direct extension of Anthropocene records. These results reveal multiple large isotopic shifts in both δ15N and δ13C values similar to or larger in magnitude to those reported in the last 150 yrs. This shows that large fluctuations in the isotopic composition of export production in this region are not unique to the recent past, but have occurred multiple times through the Mid- to Late-Holocene. However, these earlier isotopic shifts occurred over much longer time intervals (∼millennial vs. decadal timescales). Further, the δ15N data confirm that the extremely low present day δ15N values recorded by deep sea corals (∼8‰) are unprecedented for the NPSG, at least within the past five millennia. Together these records reveal centennial to millennial-scale oscillations in NPSG biogeochemical cycles. Further, these data also suggest a number of independent biogeochemical regimes during which δ15N and δ13C trends were synchronous (similar to recent coral records) or distinctly decoupled. We propose that phytoplankton species composition and nutrient source changes are the dominant mechanisms controlling the coupling and de-coupling of δ15N and δ13C values, likely primarily influenced by changing oceanographic conditions (e.g., stratification vs. entrainment). The decoupling observed in the past further suggests that oceanographic forcing and ecosystem responses controlling δ15N and δ13C values of export production have been substantially different earlier in the Holocene compared to mechanisms controlling the present day system

Carbon and nitrogen isotope fractionation of amino acids in an avian marine predator, the gentoo penguin (Pygoscelis papua)

© The Author(s), 2015. This article is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in Ecology and Evolution 5 (2015): 1278–1290, doi:10.1002/ece3.1437.Compound-specific stable isotope analysis (CSIA) of amino acids (AA) has rapidly become a powerful tool in studies of food web architecture, resource use, and biogeochemical cycling. However, applications to avian ecology have been limited because no controlled studies have examined the patterns in AA isotope fractionation in birds. We conducted a controlled CSIA feeding experiment on an avian species, the gentoo penguin (Pygoscelis papua), to examine patterns in individual AA carbon and nitrogen stable isotope fractionation between diet (D) and consumer (C) (Δ13CC-D and Δ15NC-D, respectively). We found that essential AA δ13C values and source AA δ15N values in feathers showed minimal trophic fractionation between diet and consumer, providing independent but complimentary archival proxies for primary producers and nitrogen sources respectively, at the base of food webs supporting penguins. Variations in nonessential AA Δ13CC-D values reflected differences in macromolecule sources used for biosynthesis (e.g., protein vs. lipids) and provided a metric to assess resource utilization. The avian-specific nitrogen trophic discrimination factor (TDFGlu-Phe = 3.5 ± 0.4‰) that we calculated from the difference in trophic fractionation (Δ15NC-D) of glutamic acid and phenylalanine was significantly lower than the conventional literature value of 7.6‰. Trophic positions of five species of wild penguins calculated using a multi-TDFGlu-Phe equation with the avian-specific TDFGlu-Phe value from our experiment provided estimates that were more ecologically realistic than estimates using a single TDFGlu-Phe of 7.6‰ from the previous literature. Our results provide a quantitative, mechanistic framework for the use of CSIA in nonlethal, archival feathers to study the movement and foraging ecology of avian consumers.This research was funded by National Science Foundation Office of Polar Programs [grants ANT-0125098, ANT-0739575] and the 2013 Antarctic Science Bursaries

Calibrating amino acid δ\u3csup\u3e13\u3c/sup\u3eC and δ\u3csup\u3e15\u3c/sup\u3eN offsets between polyp and protein skeleton to develop proteinaceous deep-sea corals as paleoceanographic archives.

Compound-specific stable isotopes of amino acids (CSI-AA) from proteinaceous deep-sea coral skeletons have the potential to improve paleoreconstructions of plankton community composition, and our understanding of the trophic dynamics and biogeochemical cycling of sinking organic matter in the Ocean. However, the assumption that the molecular isotopic values preserved in protein skeletal material reflect those of the living coral polyps has never been directly investigated in proteinaceous deep-sea corals. We examined CSI-AA from three genera of proteinaceous deep-sea corals from three oceanographically distinct regions of the North Pacific: Primnoa from the Gulf of Alaska, Isidella from the Central California Margin, and Kulamanamana from the North Pacific Subtropical Gyre. We found minimal offsets in the δ13C values of both essential and non-essential AAs, and in the δ15N values of source AAs, between paired samples of polyp tissue and protein skeleton. Using an essential AA δ13C fingerprinting approach, we show that estimates of the relative contribution of eukaryotic microalgae and prokaryotic cyanobacteria to the sinking organic matter supporting deep-sea corals are the same when calculated from polyp tissue or recently deposited skeletal tissue. The δ15N values of trophic AAs in skeletal tissue, on the other hand, were consistently 3–4‰ lower than polyp tissue for all three genera. We hypothesize that this offset reflects a partitioning of nitrogen flux through isotopic branch points in the synthesis of polyp (fast turnover tissue) and skeleton (slow, unidirectional incorporation). This offset indicates an underestimation, albeit correctable, of approximately half a trophic position from gorgonin protein-based deep-sea coral skeleton. Together, our observations open the door for applying many of the rapidly evolving CSI-AA based tools developed for metabolically active tissues in modern systems to archival coral tissues in a paleoceanographic context

On the creation of thermal equations of state for use in Dioptas

Dioptas is a widely used software package for integrating and analysing 2-dimensional diffraction images. To help interpret the integrated diffraction profiles it produces, Dioptas users can input files that parameterise a material's thermal equation of state (EoS), enabling the positions of the Bragg peaks from that material to be calculated as a function of pressure and temperature. However, care is needed to ensure that these input files correctly describe the thermal EoS of interest. Here we describe the thermal EoS model used by Dioptas and show how existing thermal EoS should be reparameterised so as to be used correctly in Dioptas. Input EoS files suitable for use with Dioptas are provided for the following commonly-used pressure calibrants and pressure transmitting media: Al, Au, Cu, Mo, Nb, Pt, Ta, hcp-Fe, MgO, NaCl-B1, NaCl-B2, KCl-B2, and Ne.</p

Contributions of gut bacteria to Bacillus thuringiensis-induced mortality vary across a range of Lepidoptera

Abstract Background Gut microbiota contribute to the health of their hosts, and alterations in the composition of this microbiota can lead to disease. Previously, we demonstrated that indigenous gut bacteria were required for the insecticidal toxin of Bacillus thuringiensis to kill the gypsy moth, Lymantria dispar. B. thuringiensis and its associated insecticidal toxins are commonly used for the control of lepidopteran pests. A variety of factors associated with the insect host, B. thuringiensis strain, and environment affect the wide range of susceptibilities among Lepidoptera, but the interaction of gut bacteria with these factors is not understood. To assess the contribution of gut bacteria to B. thuringiensis susceptibility across a range of Lepidoptera we examined larval mortality of six species in the presence and absence of their indigenous gut bacteria. We then assessed the effect of feeding an enteric bacterium isolated from L. dispar on larval mortality following ingestion of B. thuringiensis toxin. Results Oral administration of antibiotics reduced larval mortality due to B. thuringiensis in five of six species tested. These included Vanessa cardui (L.), Manduca sexta (L.), Pieris rapae (L.) and Heliothis virescens (F.) treated with a formulation composed of B. thuringiensis cells and toxins (DiPel), and Lymantria dispar (L.) treated with a cell-free formulation of B. thuringiensis toxin (MVPII). Antibiotics eliminated populations of gut bacteria below detectable levels in each of the insects, with the exception of H. virescens, which did not have detectable gut bacteria prior to treatment. Oral administration of the Gram-negative Enterobacter sp. NAB3, an indigenous gut resident of L. dispar, restored larval mortality in all four of the species in which antibiotics both reduced susceptibility to B. thuringiensis and eliminated gut bacteria, but not in H. virescens. In contrast, ingestion of B. thuringiensis toxin (MVPII) following antibiotic treatment significantly increased mortality of Pectinophora gossypiella (Saunders), which was also the only species with detectable gut bacteria that lacked a Gram-negative component. Further, mortality of P. gossypiella larvae reared on diet amended with B. thuringiensis toxin and Enterobacter sp. NAB3 was generally faster than with B. thuringiensis toxin alone. Conclusion This study demonstrates that in some larval species, indigenous gut bacteria contribute to B. thuringiensis susceptibility. Moreover, the contribution of enteric bacteria to host mortality suggests that perturbations caused by toxin feeding induce otherwise benign gut bacteria to exert pathogenic effects. The interaction between B. thuringiensis and the gut microbiota of Lepidoptera may provide a useful model with which to identify the factors involved in such transitions.http://deepblue.lib.umich.edu/bitstream/2027.42/112871/1/12915_2008_Article_219.pd

Divergent trophic responses of sympatric penguin species to historic anthropogenic exploitation and recent climate change

The Southern Ocean is in an era of significant change. Historic overharvesting of marine mammals and recent climatic warming have cascading impacts on resource availability and, in turn, ecosystem structure and function. We examined trophic responses of sympatric chinstrap (Pygoscelis antarctica) and gentoo (Pygoscelis papua) penguins to nearly 100 y of shared environmental change in the Antarctic Peninsula region using compound-specific stable isotope analyses of museum specimens. A century ago, gentoo penguins fed almost exclusively on low-trophic level prey, such as krill, during the peak of historic overexploitation of marine mammals, which was hypothesized to have resulted in a krill surplus. In the last 40 y, gentoo penguin trophic position has increased a full level as krill declined in response to recent climate change, increased competition from recovering marine mammal populations, and the development of a commercial krill fishery. A shifting isotopic baseline supporting gentoo penguins suggests a concurrent increase in coastal productivity over this time. In contrast, chinstrap penguins exhibited no change in trophic position, despite variation in krill availability over the past century. The specialized foraging niche of chinstrap penguins likely renders them more sensitive to changes in krill availability, relative to gentoo penguins, as evinced by their declining population trends in the Antarctic Peninsula over the past 40 y. Over the next century, similarly divergent trophic and population responses are likely to occur among Antarctic krill predators if climate change and other anthropogenic impacts continue to favor generalist over specialist species

Biofuel Feedstock Assessment for Selected Countries

Findings from biofuel feedstock production assessments and projections of future supply are presented and discussed. The report aims to improve capabilities to assess the degree to which imported biofuel could contribute to meeting future U.S. targets to reduce dependence on imported oil. The study scope was focused to meet time and resource requirements. A screening process identified Argentina, Brazil, Canada, China, Colombia, India, Mexico, and the Caribbean Basin Initiative (CBI) region for initial analysis, given their likely role in future feedstock supply relevant to U.S. markets. Supply curves for selected feedstocks in these countries are projected for 2012, 2017 and 2027. The supply functions, along with calculations to reflect estimated supplies available for export and/or biofuel production, were provided to DOE for use in a broader energy market allocation study. Potential cellulosic supplies from crop and forestry residues and perennials were also estimated for 2017 and 2027. The analysis identified capacity to potentially double or triple feedstock production by 2017 in some cases. A majority of supply growth is derived from increasing the area cultivated (especially sugarcane in Brazil). This is supplemented by improving yields and farming practices. Most future supplies of corn and wheat are projected to be allocated to food and feed. Larger shares of future supplies of sugarcane, soybean and palm oil production will be available for export or biofuel. National policies are catalyzing investments in biofuel industries to meet targets for fuel blending that generally fall in the 5-10% range. Social and environmental concerns associated with rapid expansion of feedstock production are considered. If the 2017 projected feedstock supply calculated as ‘available’ for export or biofuel were converted to fuel, it would represent the equivalent of about 38 billion gallons of gasoline. Sugarcane and bagasse dominate the available supply, representing 64% of the total. Among the nations studied, Brazil is the source of about two-thirds of available supplies, followed distantly by Argentina (12%), India and the CBI region

Optical modeling and polarization calibration for CMB measurements with ACTPol and Advanced ACTPol

The Atacama Cosmology Telescope Polarimeter (ACTPol) is a polarization sensitive upgrade to the Atacama Cosmology Telescope. Located at an elevation of 5190 m, ACTPol measures the Cosmic Microwave Background (CMB) temperature and polarization with arcminute-scale angular resolution. Calibration of the detector angles is a critical step in producing maps of the CMB polarization. Polarization angle offsets in the detector calibration can cause leakage in polarization from E to B modes and induce a spurious signal in the EB and TB cross correlations, which eliminates our ability to measure potential cosmological sources of EB and TB signals, such as cosmic birefringence. We present our optical modeling and measurements associated with calibrating the detector angles in ACTPol.Comment: 12 pages, 8 figures, conference proceedings submitted to Proceedings of SPIE; added reference in section 2 and merged repeated referenc